Absorbable block copolymers and surgical articles fabricated therefrom

Abstract

Block copolymers have one of the block made from hard phase forming monomers and another block made from soft phase forming monomers copolymerized with randomly intermingled units of other soft phase forming monomers. Particularly useful copolymers are initiated with a polyalkylene oxide initiator. The copolymers are useful in forming surgical articles, including both monofilament and multifilament sutures.

What is claimed is: 
     
       1. A block copolymer comprising: a) a polyalkylene oxide block;   b) at least one block containing a proportion of glycolic acid ester units; and   c) at least one other block comprising 1,4 dioxan-2-one randomly polymerized with 1,3 dioxane-2-one.   
     
     
       2. The block copolymer of claim 1, wherein glycolic acid ester units comprise from about 50 to about 80 percent by weight of said block copolymer. 
     
     
       3. The block copolymer of claim 1, wherein said blocks comprising random copolymers of 1,4 dioxan-2-one and 1,3 dioxane-2-one comprise from about 20 to about 50 percent by weight of said block copolymer. 
     
     
       4. The block copolymer of claim 3, wherein said blocks comprising random copolymers of 1,4 dioxan-2-one and 1,3 dioxane-2-one are formed from the random polymerization of about 35 percent by weight of 1,4 dioxan-2-one and about 65 percent by weight 1,3 dioxane-2-one. 
     
     
       5. The block copolymer of claim 1, wherein component (b) comprises a predominant amount of glycolic acid ester units, the remainder being 1,4 dioxane-2-one. 
     
     
       6. The block copolymer of claim 5 wherein component (c) consists essentially of 1,4 dioxane-2-one randomly polymerized with 1,3 dioxane-2-one. 
     
     
       7. The block copolymer according to claim 1, wherein said polyalkylene oxide block is formed from an initiator selected from the group consisting of polyethylene oxide, polypropylene oxide, diethylene glycol, polyethylene glycol, polyethylene glycol diol, polyethylene glycol methyl ether, polypropylene glycol and copolymers of ethylene oxide and propylene oxide. 
     
     
       8. The block copolymer of claim 1, wherein said block copolymer is a penta-block copolymer. 
     
     
       9. The block copolymer of claim 8, wherein said polyalkylene oxide block is the center block; at least one of said blocks comprising 1,4 dioxan-2-one randomly polymerized with 1,3 dioxane-2-one is adjacent said center block; and at least one of said blocks containing a proportion of glycolic acid ester units is adjacent said blocks comprising 1,4 dioxan-2-one randomly polymerized with 1,3 dioxane-2-one. 
     
     
       10. A surgical article formed totally or in part from the block copolymer of claim 1. 
     
     
       11. The surgical article of claim 10, wherein said surgical article is selected from the group consisting of clips, staples, sutures, pins, screws, prosthetic devices, anastomosis rings, and growth matrices. 
     
     
       12. The surgical article of claim 10, wherein said surgical article is a suture which retains its in vivo tensile strength for about 14 days. 
     
     
       13. A method of making a copolymer comprising the steps of: a) adding 1,4 dioxane-2-one and 1,3 dioxane-2-one to a reactor;   b) polymerizing component (a) in the presence of a polyalkylene oxide initiator to the point where all the 1,3 dioxane-2-one is incorporated in a polymer but residual 1,4 dioxane-2-one monomer remains;   c) adding glycolide; and   d) polymerizing.   
     
     
       14. The method according to claim 13, wherein said polyalkylene oxide initiator is selected from the group consisting of polyethylene oxide, polypropylene oxide, diethylene glycol, polyethylene glycol, polyethylene glycol diol, polyethylene glycol methyl ether, polypropylene glycol and copolymers of ethylene oxide and propylene oxide. 
     
     
       15. A copolymer obtained in accordance with the method of claim 13. 
     
     
       16. A suture fabricated from a copolymer, said copolymer comprising: a) a polyalkylene oxide center block;   b) at least one block containing a proportion of glycolic acid ester units; and   c) at least one other block comprising 1,4 dioxan-2-one randomly polymerized with 1,3 dioxane-2-one.   
     
     
       17. The suture of claim 16 exhibiting in vivo tensile strength retention for about 14 days. 
     
     
       18. The suture of claim 16 which is a monofilament suture. 
     
     
       19. A method of suturing a wound comprising: a) providing a needled suture, the suture being fabricated from a block copolymer comprising: i) a center block of polyalkylene oxide,   ii) at least one block containing a proportion of glycolic acid ester units, and   iii) at least one other block comprising 1,4 dioxan-2-one randomly polymerized with 1,3 dioxane-2-one; and     b) passing said needled suture through tissue to create wound closure.